1. Field of the Invention
The invention relates to a method of producing monocrystalline layers on a substrate.
2. Prior Art
Production of thin layer components, such as MOS components in semiconductor technology or IC components in SOS (silicon-on-sapphire) technology, etc., require processes whereby monocrystalline layers and/or a sequence of semiconductive layers can be deposited on a monocrystalline or an amorphous substrate. Known methods for producing such thin layers or such layer sequences generally comprise high-temperature processes in which a semiconductor material is epitaxial deposited on a substrate from a suitable gas phase or in which epitaxial deposition takes place on a seed from a liquid phase and large band or cylindrically shaped monocrystalline bodies are pulled therefrom and subsequently divided or disked into individual wafers or layers. Deposition of a thin layer from a gas phase may be accomplished by a so-called "ion plating" technique wherein a substrate to be coated with a layer is exposed to ion bombardment in order to cleanse the substrate surface, located within a suitable chamber which may be under vacuum. The material to be deposited as the layer is positioned in a crucible which is in working association with the cleansed substrate surface and upon energization of the crucible, the material therein is vaporized and precipitates or is deposited on the substrate surface. Ion bombardment may be maintained throughout the vapor-deposition process so as to improve adhesion between the deposited film and the substrate surface. Orientated growth of a so-deposited film may also be attained under these conditions (see "J. Vac. Sci. Technology", Vol. 10 (1973) pages 47-52). Since epitaxial growth proceeds via a seed or nuclei formation in such layers and subsequently proceeds as an orientated growth on such seeds, it is necessary in this "ion-plating" process to insure that a sufficient surface diffusion of the vaporized particles takes place on the substrate surface. In the prior art process, this is accomplished by utilizing a relatively high temperature on the substrate. Moreover, in most cases, this prior art process requires the use of a monocrystalline substrate which has a lattice structure similar to the lattice structure of the layer being grown so that an orientation is already determined during the nuclei formation. However, such high substrate temperatures are disadvantageous when, for example, the substrate per se is a semiconductor layer having dopant zones therein since dopant penetration and dopant peripheries are altered at high temperatures due to diffusion phenomena. Further, it is often times desirable to form layers on substrates which are not monocrystalline or have a lattice structure different from that of the layer being deposited.